Numerical Simulation Study Of Ultra-low Nitrogen Sidewall Gas Burner

With the increasingly stringent emission requirements and the increasing awareness of environmental protection,gas has received widespread attention as a clean and efficient energy source.However,the combustion of gas still has problems such as greater pollution of nitrogen oxides.Based on this,according to the combustion characteristics of the sidewall gas burner of an ethylene combustion cracking furnace in a petrochemical industry,the operation and structural parameters of the sidewall gas burner on the combustion process and NO_x emissions were studied.Due to the large reaction equipment and high reaction temperature of the burner,it is difficult to achieve economic and efficient research on the combustion process using conventional experimental methods.Therefore,this paper uses a numerical simulation calculation method to start from a single sidewall burner to study the sidewall gas burner.The specific combustion conditions under different operating parameters and structural parameters are also explored and analyzed for key parameters such as temperature field and NO_X concentration distribution.First,the thesis rationalizes the structure of the sidewall burner,and models the burner(SOLIDWORKS)and grid division(Pointwise).In order to further simulate the real combustion situation,the paper analyzes and selects the required numerical model,using Realizable k-?turbulence model,EDC combustion model and other model parameters.Through numerical simulation calculation(FLUENT),the effect of the sidewall burner on NO_X emissions under three different operating conditions,such as different heat load,excess air coefficient and the ratio of primary and secondary air rates,etc.,is obtained.The research results show that the thermal NO_X emissions are affected by both the burner heat load and the burner temperature,When the heat load of the burner increases,the thermal NO_X emissions show a linear decreasing relationship;when the excess air coefficient is greater than 1.1,a large amount of cold air enters to reduce the temperature of the burner room,and the thermal NO_Xconcentration value gradually decreases;when the fuel is fully burned,increasing the proportion of primary air rate in an appropriate amount can effectively reduce the temperature in the burner,thereby also reducing the generation of thermal NO_X.Secondly,the paper optimizes the combustion performance of the sidewall burner by changing the structural parameters of the primary premixed nozzle and the secondary fuel pipe.The results of the study show that when the width of the primary premixed nozzle is?=8 mm,the NO_X concentration distribution on the center section of the sidewall burner is the lowest;opening the secondary air nozzle can achieve air staged combustion,which is beneficial to reduce the emission of nitrogen oxide;When the number of secondary fuel gas nozzles is adjusted to 4 and the nozzle angular spacing is 55°,the NO_X emission is 57.6 ppm,which can achieve low nitrogen combustion;in addition,the increase of the secondary fuel gas nozzle angle is conducive to the uniform dispersion of the flame,to achieve low NO_X emissions requirements.In addition,the paper also uses the‘internal circulation+air classification'combustion technology to improve and optimize the structure of the sidewall burner.In the end,the NO_Xemissions were reduced to a certain extent-26.7 ppm,and the target of emissions below 30 ppm was achieved.